sql - Which one have better performance : Derived Tables or Temporary Tables

Question

Sometimes we can write a query with both derived table and temporary table. my question is that which one is better? why?

Answer 1

Derived table is a logical construct.

It may be stored in the tempdb, built at runtime by reevaluating the underlying statement each time it is accessed, or even optimized out at all.

Temporary table is a physical construct. It is a table in tempdb that is created and populated with the values.

Which one is better depends on the query they are used in, the statement that is used to derive a table, and many other factors.

For instance, CTE (common table expressions) in SQL Server can (and most probably will) be reevaluated each time they are used. This query:

WITH    q (uuid) AS
        (
        SELECT  NEWID()
        )
SELECT  *
FROM    q
UNION ALL
SELECT  *
FROM    q

will most probably yield two different NEWID()'s.

In this case, a temporary table should be used since it guarantees that its values persist.

On the other hand, this query:

SELECT  *
FROM    (
        SELECT  *, ROW_NUMBER() OVER (ORDER BY id) AS rn
        FROM    master
        ) q
WHERE   rn BETWEEN 80 AND 100

is better with a derived table, because using a temporary table will require fetching all values from master, while this solution will just scan the first 100 records using the index on id.